Although pesticide use in agriculture is on the rise, some farms have switched to organic practices and shy away from applying them. Yet there is a question not just a little. And the question is, can chemicals that ended up in the soil decades ago continue to affect the soil even after switching to organic crops?
Today a research team (as reported in Environmental Science & Technology) identified pesticide residues in 100 Swiss farms. Including fields dedicated to organic farming. Beneficial soil microbes are adversely affected by crop remnants that are up to many years old.
Because organic farming is much, much healthier
Fungicides, herbicides and pesticides protect crops by repelling or destroying organisms that damage plants. On the contrary, organic farming management strategies avoid the addition of synthetic substances, relying instead on the natural ecosystem of the soil. As long as it's healthy, though!
Some organic farms operate on land previously treated with pesticides. And, as mentioned, it is not clear whether pesticides have a lasting presence in organically managed fields and what the consequences are for the life of the soil. In particular, those on beneficial soil microbes and fungi leave great doubts, they seem to be negatively influenced by pesticides even years after their application. As if the microplastics, now everywhere.
Research on the persistence of pesticides
Judith Riedo, Thomas Bucheli, Florian Walder, Marcel van der Heijden and colleagues wanted to examine pesticide levels and their impact on soil health on conventional versus organic farms, as well as farms converted to organic methods.
The team measured surface soil characteristics and concentrations of 46 regularly used pesticides. It also monitored the substances produced by their degradation, and they did so by analyzing samples taken from as many as 100 fields managed with conventional or biological practices.
Surprisingly, the researchers found pesticide residues at all sites, including organic farms converted more than 20 years earlier.
A long curse
At least one fungicide and more herbicides remained in the surface soil after conversion to organic practices. Although the total number of pesticide residues decreases the longer the field is managed with organic practices, this is a worrying factor.
There is also the hypothesis of a "return" contamination: according to the researchers, some of the pesticides may have contaminated organic fields by traveling through the air, water or soil from nearby conventional fields. Additionally, the team observed lower microbial abundance and decreased levels of a beneficial microbe when the fields had more pesticides in the fields, suggesting that the presence of these substances may decrease soil health.
The researchers say future work should examine the synergistic effects of pesticide residues and other environmental stressors on soil health.